The lower esophageal sphincter (LES) in healthy individuals allows food to pass into the stomach, but prevents gastric fluids from moving into the esophagus except when the patient vomits. Aspiration and gastroesophageal reflux disease (GERD) are clinical risks for patients having a malfunctioning LES or for patients having stents placed across the LES so that the LES remains open. Aspiration occurs when the stomach contents travel from the stomach into the lungs. Aspiration in the lungs can lead to pneumonia or death. GERD produces heartburn, abdominal pain and regurgitation of the stomach contents into the esophagus and pharynx. GERD may lead to the alteration of the lining of the esophagus that results in Barrett's Esophagus and may progress to esophageal cancer. Risk of aspiration and GERD in patients having a compromised LES increases when the patient is in a prone position.
Anti-reflux esophageal prostheses or stents have been developed to treat tumors or strictures in the vicinity of the LES. An anti-reflux esophageal prosthesis or stent is typically placed in the lower esophagus and through the LES to maintain the patency thereof due to the presence of a cancerous tumor commonly found in the vicinity thereof or to treat benign tumor conditions, such as blockage or strictures.
A problem with an esophageal prosthesis or stent is that fluid from the stomach flows into the mouth of the patient when in a prone position, increasing the risk of aspiration and reflux. In an attempt to solve the problem, a number of esophageal prostheses or stents utilize a one-way valve in which only food or fluid from the esophagus flows into the stomach in only an antegrade or forward direction. However, these one-way anti-reflux prostheses or stents present another problem. When the patient wants to belch or vomit, the patient is prevented from doing so, because the one-way valve prevents backward flow in the retrograde direction. Such a condition is not only painful to the patient, but can also lead to more complicated medical conditions. Other inverting valves can invert with pressure at which the patient coughs or belches that allows some reflux, however, these designs do not readily revert back to the original position.
What is needed is a prosthesis that allows food to pass into the stomach and prevents gastric fluids from entering the esophagus, yet allows for vomiting and belching when necessary.